Damper system for transportation

ABSTRACT

A damper system for transportation includes a packaging box for storing a container containing a work and also includes a pair of an upper damper and a lower damper each placed between the packaging box and the container. The upper and lower dampers contain foamed polyethylene or polypropylene, the upper damper includes upper impact-absorbing sections, and the lower damper includes lower impact-absorbing sections. The sum of h 2  and h 1  is equal to the width of an upper or lower space between the packaging box and the container, and h 1  is greater than h 2 , wherein h 2  represents the height of the upper impact-absorbing sections and h 1  represents the height of the lower impact-absorbing sections. The shape of the upper and lower impact-absorbing sections is rectangular parallelepiped shape.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims, under 35 USC 119, priority of JapaneseApplication No. 2003-200935 filed Jul. 24, 2003.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to packaging systems for transportingcontainers principally storing circular works such as semiconductorwafers or magnetic disks. The present invention particularly relates toa damper system for transportation. The damper system includes apackaging box, such as a corrugated fiberboard box, for storing acontainer containing a work and also includes a pair of upper and lowerdampers placed between the container and the packaging box. The dampersabsorb impact applied from outside, whereby the container and the workplaced therein are prevented from being damaged.

2. Description of the Related Art

FIG. 4 shows a known damper system for transporting semiconductor wafersor recording disks. The known damper system includes a packaging box 1including a corrugated fiberboard; a lower damper 2, placed on a bottomsection of the packaging box 1, having a recessed retaining portion 4; acontainer 5, made of plastic or resin, storing several tens ofsemiconductor wafers or recording disks; and an upper damper 3 placed onthe container 5. The container 5 is retained with the recessed retainingportion 4 in a fitted manner and placed between the lower damper 2 andthe upper damper 3. The packaging box 1 is sealed with staples or astrip of adhesive tape. Therefore, the container 5 is protected fromimpact applied from outside during the transportation thereof andtherefore prevented from being injured or damaged, and the semiconductorwafers or the recording disks placed in the container 5 are alsoprevented from being injured or damaged.

The lower and upper dampers 2 and 3 principally include a molded articlemade of a thin plastic sheet; a foam-molded article made ofpolyethylene, polypropylene, or polyurethane; or a laminated corrugatedfiberboard. Those materials can be readily distorted by impact andcannot be readily restored to their former state; hence, the lower andupper dampers 2 and 3, once distorted, cannot absorb impact continuouslyapplied thereto.

Japanese Unexamined Patent Application Publication No. 2000-208602discloses a shipping box that is partly reusable and hardly propagatesimpact. The shipping box is made of metal and includes a cushioningmaterial placed therein. However, the shipping box is not suitable forpractical use because the usage cost is high unless the box is fullyreused.

On the other hand, large-diameter semiconductor wafers with a diameterof 300 mm have a weight at least twice greater than that of knownsemiconductor wafers with a diameter of 200 mm. Therefore, containersfor storing the large-diameter semiconductor wafers have a large weight.Increase in the diameter of semiconductor wafers causes a decrease inthe strength of the wafers; hence, a slight impact that does not causedamage in the 200-mm wafers during the transportation causes seriousdamage in the 300-mm wafers during the transportation in some cases.

For example, Japanese Unexamined Patent Application Publication No.2002-160769 discloses a bellows, which is one of dampers for containersthat do not cause an increase in the volume or size of packages andabsorb impact, the bellows being made of a molded sheet containingpolypropylene or polyethylene. However, the bellows has an insufficientability to absorb impact and cannot therefore be used for transportingthe 300 mm wafers.

In general, molded plastic sheets and laminated corrugated fiberboardsused in known techniques have low resilience. Therefore, once the sheetsand the fiberboards receive a strong impact, they are distorted andcannot function as dampers. Dampers made of foamed polyurethane can berestored to its former state if the dampers receive impact. However, inthe dampers, there is a problem in that poisonous gas is generated whenthe dampers discarded are burned.

The inventors have investigated the ability to absorb impact, theresilience, and the disposal problem, found that foamed polyethylene andpolypropylene are the best materials for forming dampers, and thendeveloped a new type of damper that is suitable for transporting alarge-diameter semiconductor wafer with a diameter of 300 mm.

Dampers containing foamed polyethylene or polypropylene will now bedescribed with reference to FIGS. 4, 5, and 6. FIG. 5 a is a plan viewshowing an upper damper 3 and FIG. 5 b is a sectional view showing theupper damper 3 taken along the line C-C′ of FIG. 5 a. FIG. 6 a is a planview showing a lower damper 2 and FIG. 6 b is a sectional view showingthe lower damper 2 taken along the line C-C′ of FIG. 6 a and a portionof the lower damper 2 in an enlarged manner.

The upper damper 3 includes eight first impact-absorbing sections 6 andfour upper impact-absorbing sections 7. The front, rear, right, and leftfaces of the upper damper 3 each have two of the eight firstimpact-absorbing sections 6 thereon and the upper face of the upperdamper 3 has the upper impact-absorbing sections 7 each placed atcorresponding predetermined regions (regions each corresponding to thecorners of a container 5) each located close to the four corners of theupper face. When impact is applied to the upper damper 3 in a direction,some of the first impact-absorbing sections 6 and upper impact-absorbingsections 7 are pressed and thereby distorted, whereby the applied impactis absorbed. The upper damper 3 has a container-retaining section, lyingover the container 5 with a size specified in the SEMI standard (M31),for retaining each of various types of containers. The lower damper 2 aswell as the upper damper 3 include eight second impact-absorbingsections 9 and four lower impact-absorbing sections 10. The front, rear,right, and left faces of the lower damper 2 each have two of the eightsecond impact-absorbing sections 9 thereon and the lower face of thelower damper 2 has the lower impact-absorbing sections 10 each placed atcorresponding predetermined regions (regions each corresponding to thecorners of the container 5) each located close to the four corners ofthe lower face. When impact is applied to the lower damper 2 in adirection, some of the second impact-absorbing sections 9 and lowerimpact-absorbing sections 10 are pressed and thereby distorted, wherebythe applied impact is absorbed.

The upper and lower impact-absorbing sections 7 and 10 have the sameheight and shape, trapezoidal, the height of the upper impact-absorbingsections 7 being represented by h1 and that of the lowerimpact-absorbing sections 10 being represented by h2. Therefore, when astrong impact is applied to the lower and upper dampers 2 and 3 in thelower direction, the lower and upper dampers 2 and 3 cannot sufficientlyabsorb the impact.

SUMMARY OF THE INVENTION

In view of the foregoing circumstances, the present invention has beenmade to enhance the ability to absorb impact and the resilience and madeto cope with the disposal problem. It is an object of the presentinvention to provide a damper system for transporting a semiconductorwafer or the like. The damper system protects a product, stored in acontainer placed in a packaging box having a predetermined size, from astrong impact applied to the packaging box particularly in the lowerdirection during the transportation of the product.

In order to achieve the above object, a damper system for transportationaccording to the present invention includes a packaging box for storinga container containing a work and also includes a pair of an upperdamper and a lower damper each placed between the packaging box and thecontainer. The upper and lower dampers contain foamed polyethylene orpolypropylene. The upper damper includes upper impact-absorbing sectionsand the lower damper includes lower impact-absorbing sections. The sumof h2 and h1 is equal to the width of an upper or lower space betweenthe packaging box and the container, and h1 is greater than h2, where h2represents the height of the upper impact-absorbing sections and h1represents the height of the lower impact-absorbing sections.

In the damper system, h1 is within a range of 4 to 5 cm and h2 is withina range of 0.5 to 1.5 cm.

In the damper system, the lower impact-absorbing sections have arectangular parallelepiped shape.

In the damper system, the lower damper has an opening for distributingimpact, applied from outside, to the lower impact-absorbing sections,the opening being located at the center of the lower damper.

In the damper system, the percentage of Sb to Sa is within a range of 3%to 5%, wherein Sa represents the area of the upper or lower face of thepackaging box and Sb represents the area of each of contact portionsbetween the packaging box and the upper impact-absorbing sections or thelower impact-absorbing sections.

Since the upper and lower dampers contain foamed polyethylene orpolypropylene and the height of the lower impact-absorbing sections isgreater than that of the upper impact-absorbing sections, the dampersystem absorbs impact applied in the lower direction and the containeror semiconductor wafers placed in the container can therefore beprevented from being damaged if the damper system is dropped from thetop of triple-stacked cargo or dropped at a height of 1.5 m or moreduring the transportation.

The lower impact-absorbing sections have a rectangular parallelepipedshape, whereas known impact-absorbing sections have a trapezoidal shape.Therefore, when a strong impact is applied to the impact-absorbingsections, the impact-absorbing sections are uniformly distorted, wherebythe impact is efficiently absorbed. Furthermore, the lower damper hasthe opening located at the center thereof, whereby the contact areabetween the container and the lower damper is minimized and an appliedimpact is distributed. Therefore, the damper system has a high abilityto absorb impact.

The lower impact-absorbing sections preferably have a height of 4 to 5cm. When the height is less than 4 cm, the impact-absorbing ability islow. In contrast, when the height is more than 5 cm, the upperimpact-absorbing sections have an insufficient height because thepackaging box has a predetermined size. Thus, the height of the lowerimpact-absorbing sections is preferably 4 to 5 cm in consideration ofthe minimum height of the upper impact-absorbing sections. The dampersystem preferably has a recessed portion so as to retain various typesof containers specified in the SEMI standard.

Since the lower damper has the opening located at the center thereof,impact applied from outside is distributed to the lower impact-absorbingsections because the impact is prevented from being propagated to theopening. Therefore, the lower impact-absorbing sections absorb theimpact and the semiconductor wafers in the container are prevented frombeing damaged.

When the upper impact-absorbing sections have such a size that an upperspace between the container and the packaging box is occupied with theupper impact-absorbing sections or the lower impact-absorbing sectionshave such a size that a lower space between the container and thepackaging box is occupied with the lower impact-absorbing sections, theupper and lower impact-absorbing sections are not distorted by impactapplied from outside and the impact is directly propagated to thecontainer. In contrast, when the contact portions between the packagingbox and the upper impact-absorbing sections or the lowerimpact-absorbing sections have an extremely small area, the upper andlower impact-absorbing sections cannot endure impact and are thereforebuckled, that is, the upper and lower dampers do not function well.Thus, the percentage of Sb to Sa is preferably within a range of 3% to5% in view of the above.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing a damper system of the presentinvention;

FIG. 2 a is a plan view showing an upper damper according to the presentinvention;

FIG. 2 b is a sectional view showing the upper damper taken along theline C-C′ of FIG. 2 a;

FIG. 3 a is a plan view showing a lower damper according to the presentinvention;

FIG. 3 b is a sectional view showing the lower damper taken along theline C-C′ of FIG. 3 a and a portion of the lower damper in an enlargedmanner;

FIG. 4 is a sectional view showing a known damper system;

FIG. 5 a is a plan view showing a known upper damper;

FIG. 5 b is a sectional view showing the known upper damper taken alongthe line C-C′ of FIG. 5 a;

FIG. 6 a is a plan view showing a known lower damper;

FIG. 6 b is a sectional view showing the known lower damper taken alongthe line C-C′ of FIG. 6 a and a portion of the known lower damper in anenlarged manner;

FIG. 7 is a graph showing impact values determined in a drop test inwhich the height of lower impact-absorbing sections and the drop heightare varied; and

FIG. 8 is a graph showing impact values determined in a drop test inwhich the drop height is varied.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A damper system for transportation according to an embodiment of thepresent invention will now be described with reference to theaccompanying drawings. Since the damper system of this embodiment hassubstantially the same configuration as that of the known damper systemdescribed above, the same components have the same reference numeralsand descriptions of the components are omitted. In this embodiment, thedamper system is described using a system, used for transporting acontainer containing a semiconductor wafer, as an example. The dampersystem includes a packaging box 1 and a pair of a lower damper 2 and anupper damper 3.

With reference to FIG. 1, a container 5 stores semiconductor wafers W,for example, 25 silicon wafers, having a diameter of 300 mm, preparedaccording to the following procedure: a silicon ingot prepared by theCzochralski process is shaped into a block having a predetermined size,the block is sliced into sheets, and the sheets are chamfered, lapped,etched, and then polished. Other components shown in FIG. 5 aresubstantially the same as those shown in FIG. 4 and have the samereference numerals as those shown in FIG. 4, and descriptions of thecomponents are omitted.

The upper damper 3 includes eight first impact-absorbing sections 6 andfour upper impact-absorbing sections 7A. The front, rear, right, andleft faces of the upper damper 3 each have two of the eight firstimpact-absorbing sections 6 thereon and the upper face of the upperdamper 3 has the upper impact-absorbing sections 7A each placed atcorresponding predetermined regions (regions each corresponding to thecorners of the container 5) each located close to the four corners ofthe upper face. When impact is applied to the upper damper 3 in adirection, some of the first impact-absorbing sections 6 and upperimpact-absorbing sections 7A are pressed and thereby distorted, wherebythe applied impact is absorbed. The upper impact-absorbing sections 7Ahave a rectangular parallelepiped shape and a height of 0.5 to 1.5 cm,the height being represented by h2.

The upper damper 3 has a container-retaining section, lying over thecontainer 5 with a size specified in the SEMI standard (M31), forretaining each of various types of containers.

The upper damper 3 has a first opening 8 located at the center thereof.The first opening 8 allows the upper damper 3 to be in contact only withouter portions of the container 5. According to such a configuration,impact applied to the upper damper 3 in the upper direction isdistributed to the upper impact-absorbing sections 7A, which aredistorted, whereby the impact is absorbed. Therefore, the semiconductorwafers W placed in the container 5 are protected from the impact.Furthermore, the first opening 8 allows observers to confirm if there isthe container 5 in the packaging box 1 and to see a label or the likeplaced on the upper face of the container 5.

The lower damper 2 as well as the upper damper 3 include eight secondimpact-absorbing sections 9 and four lower impact-absorbing sections10A. The front, rear, right, and left faces of the lower damper 2 eachhave two of the eight second impact-absorbing sections 9 thereon and thelower face of the lower damper 2 has the lower impact-absorbing sections10A each placed at corresponding predetermined regions (regions eachcorresponding to the corners of the container 5) each located close tothe four corners of the lower face. The height of the lowerimpact-absorbing sections 10A is greater than that of the upperimpact-absorbing sections 7A. When impact is applied to the lower damper2 in a direction, some of the second impact-absorbing sections 9 andlower impact-absorbing sections 10A are pressed and thereby distorted,whereby the applied impact is absorbed. The lower impact-absorbingsections 10A have a rectangular parallelepiped shape and a height of 4to 5 cm, the height being represented by h1. When a strong impact isapplied to the lower impact-absorbing sections 10A, the lowerimpact-absorbing sections 10A are therefore uniformly distorted andabsorb the impact slowly, whereby the semiconductor wafers W placed inthe container 5 are prevented from being damaged. The upper face of thelower damper 2 has a recessed portion of which the bottom is flat andwhich is in contact only with a lower portion of the container 5. Theweight of the container 5 is applied only to the lower portion thereof.When impact is applied to the lower damper 2 in the lower direction,only the lower impact-absorbing sections 10A are distorted, whereby theimpact is absorbed.

The lower damper 2 has a second opening 11 located at the centerthereof. The second opening 11 has the same function as that of thefirst opening 8. That is, the second opening 11 allows the lower damper2 to be in contact only with outer portions of the container 5.According to such a configuration, impact applied to the lower damper 2in the lower direction is distributed to the lower impact-absorbingsections 10A, which are distorted, whereby the impact is absorbed. Whenthe lower impact-absorbing sections 10A are distorted due to the appliedimpact, the second opening 11 prevents the upper face of the lowerdamper 2 from being in contact with the lower face of the container 5;whereby the impact is prevented from being applied to the whole lowerface of the container 5. The percentage of Sb to Sa is preferably withina range of 3% to 5% and more preferably 4%, wherein Sa represents thearea of the upper or lower face of the packaging box 1 and Sb representsthe area of each of contact portions between the packaging box 1 and theupper impact-absorbing sections 7A or the lower impact-absorbingsections 10A.

A drop test will now be described, the test being performed using adamper system for transportation according to the present invention anda known damper system for transportation. In the test, containers eachcontaining 25 semiconductor silicon wafers with a diameter of 300 mmwere each placed in corresponding packaging boxes made of a corrugatedfiberboard, and the packaging boxes were sealed with staples or stripsof adhesive tape.

FIG. 7 shows impact values determined in a first experiment, in whichthe drop height is 1, 1.2, or 1.5 m, lower dampers and upper dampers aremade of foamed polyethylene expanded by 30 times, and the height oflower impact-absorbing sections is 4.5 cm. FIG. 8 shows impact valuesdetermined in a second experiment, in which the height of the lowerimpact-absorbing sections is 3.5, 4.0, or 4.5 cm and the drop height is1 or 1.5 m. Conditions such as the number of the stored semiconductorsilicon wafers and the material of the dampers are common to the firstand second experiments.

As is clear from FIGS. 7 and 8, the damper system of the presentinvention more effectively absorbs impact as compared with the knowndamper system. Therefore, the silicon wafers placed in the container areprevented from being damaged.

As described above, a damper system of the present invention absorbsimpact applied in the upper, lower, right, left, front, or backdirection if the system includes a packaging box with a predeterminedsize. In particular, the damper system absorbs a strong impact appliedto the system in the lower direction. Thus, semiconductor silicon wafersthat have a large diameter and are therefore very expensive can beprevented from being chipped or cracked and can be transported safelyand securely.

Examples of a material for forming the lower and upper dampers 2 and 3include foamed polyethylene, which is used in the test described below,and polypropylene.

And if the h1, the height of the upper impact-absorbing sections 7A ofthe lower damper 2, is set within the range of 4 to 5 cm, the samefunction and effect as above-described embodiment can be obtained. Inaddition, the h2, the height of the lower impact-absorbing section 10Aof the upper damper 3, is set within the range of 0.5 to 1.5 cm, thesame function and effect as above-described embodiment can be alsoobtained.

The packaging box 1 and the container 5 each have a predetermined sizeand the size is not varied; hence, the width of spaces therebetween isnot varied. Therefore, the sum of h1 and h2 is equal to the width of alower or upper space between the packaging box 1 and the container 5.

Besides it, if the percentage of the Sb, the area of each of the contactportions, to the Sa, the area of the upper or lower face of thepackaging box 1, is set within the range of 3 to 5%, the same functionand effect as above-described embodiment can be also obtained.

1. A damper system for transportation, comprising: a packaging box for storing a container containing a work; and a pair of an upper damper and a lower damper each placed between the packaging box and the container, wherein the upper and lower dampers contain foamed polyethylene or polypropylene, the upper damper includes upper impact-absorbing sections, the lower damper includes lower impact-absorbing sections, the sum of h2 and h1 is equal to the width of an upper or lower space between the packaging box and the container, and h1 is greater than h2, where h2 represents the height of the upper impact-absorbing sections and h1 represents the height of the lower impact-absorbing sections.
 2. The damper system according to claim 1, wherein h1 is within a range of 4 to 5 cm and h2 is within a range of 0.5 to 1.5 cm.
 3. The damper system according to claim 1, wherein the lower impact-absorbing sections have a rectangular parallelepiped shape.
 4. The damper system according to claim 2, wherein the lower damper has an opening for distributing impact, applied from outside, to the lower impact-absorbing sections, the opening being located at the center of the lower damper.
 5. The damper system according to claim 1, wherein the percentage of Sb to Sa is within a range of 3% to 5%, where Sa represents the area of the upper or lower face of the packaging box and Sb represents the area of each of contact portions between the packaging box and the upper impact-absorbing sections or the lower impact-absorbing sections. 